The centriole is involved in which cellular process?
A. Cell division
B. Lipid synthesis
C. Protein synthesis
D. Photosynthesis
Answer: Option A
Solution (By JKSSB Mock Tests)
Centrioles are cylindrical microtubular structures found near the nucleus in animal cells, forming the centrosome. They organize spindle fibers during cell division (mitosis and meiosis) and are also the basal bodies of cilia and flagella. They are absent in higher plant cells. Centrioles duplicate during S phase and migrate to poles during prophase.
Consider the following statements about the cell membrane:
1. It is composed of a phospholipid bilayer.
2. It is fully permeable.
3. Proteins are embedded in the membrane.
Which of the above is/are correct?
Explanation:
Sulfur is present in the amino acids methionine and cysteine (which forms disulfide bonds in proteins). Nitrogen is in all amino acids, phosphorus in nucleic acids and ATP, iron in heme. Sulfur is also in vitamins biotin and thiamine. Disulfide bonds are crucial for protein tertiary structure.
Explanation:
Chlorophyll and other photosynthetic pigments are embedded in the thylakoid membranes of chloroplasts, where they participate in light-dependent reactions. The stroma contains enzymes for the Calvin cycle. The cell wall and cytoplasm are not sites of photosynthesis.
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